It was narrated from `Ali (رضي الله عنه) :

I said: O Messenger of Allah (ﷺ), why do you marry from Quraish and not from us? He said: “Do you have anyone?` I said: The daughter of Hamzah. He said: `She is the daughter of my brother through breastfeeding.“

حَدَّثَنَا عَبْد اللَّهِ، حَدَّثَنِي مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ نُمَيْرٍ، حَدَّثَنَا أَبِي، حَدَّثَنَا الْأَعْمَشُ، عَنْ سَعْدِ بْنِ عُبَيْدَةَ، عَنْ أَبِي عَبْدِ الرَّحْمَنِ، عَنْ عَلِيٍّ، قُلْتُ يَا رَسُولَ اللَّهِ مَا لِي أَرَاكَ تَنَوَّقُ فِي قُرَيْشٍ وَتَدَعُنَا قَالَ عِنْدَكَ شَيْءٌ قُلْتُ ابْنَةُ حَمْزَةَ قَالَ هِيَ ابْنَةُ أَخِي مِنْ الرَّضَاعَةِ‏.‏